BERLIN | It's Plan B in the fight against climate change: cooling the planet by sucking heat-trapping CO2 from the air or reflecting sunlight back into space.
Called geoengineering, it's considered mad science by opponents. Supporters say it would be foolish to ignore it, since plan A — slashing carbon emissions from fossil fuels — is moving so slowly.
The U.N.'s expert panel on climate change is under pressure from both sides as it considers whether geoengineering should be part of the tool-kit that governments use to keep global warming in check.
Russia, in particular, has been pushing the panel to place more emphasis on such techniques in a key document for policymakers being finalized in Berlin.
Drafts leaked before the conference mentioned only one of the options, removing CO2 from the air and storing it underground. Russia, a major oil and gas producer, said the Intergovernmental Panel on Climate Change should also mention solar radiation management, which could include everything from covering open surfaces with reflective materials or placing sun-mirrors in orbit around the Earth.
But even advocates of studying geoengineering express doubts.
"Really at the present moment there is a high level of uncertainty surrounding all of these options," said Steve Rayner, co-director of Oxford University's geoengineering program.
"It seems like a dangerous gamble to hold up this technology that may not work," said Jim Thomas, of the Canada-based ETC Group.
However, the IPCC's draft document says that unless emissions are cut much faster than currently projected, measures to scrub CO2 from the air will be have to be deployed to avoid potentially dangerous levels of warming.
The problem is those technologies don't exist yet or are in an experimental stage. No one knows whether they will be successful.
Ideas include spraying clouds with seawater to make them more reflective or pumping aerosols into the air to mimic the cooling effect from major volcanic eruptions.
Each is associated with unknown risks, including potentially shifting weather patterns or damaging the ozone layer that protects the Earth from ultraviolet sunrays.
One technology that is currently being tested at a small scale is called "bio-energy with carbon capture and storage," or BECCS. The idea is to grow crops that absorb CO2 from the atmosphere then burn them in a power station to generate energy. The resulting CO2 emissions are captured at the plant and then stored deep underground. The net effect of that process is that CO2 is removed from the air.